1. Field of the Invention
The invention disclosed broadly relates to the field of spectroscopic analysis, and more particularly relates to the field of Raman spectroscopic analysis for the authentication of the optical and electromagnetic properties of inks, dyes, thin films, plastics, toners, paper, fixatives, paints, printing agents and other written materials.
2. Description of the Related Art
The investigation of authenticity, and in particular, the discovery of a forgery, are problems that have plagued man since antiquity. One early target of forgery was currency and many laws were passed to thwart counterfeiting. Today, fraudulent activity encompasses much more than paper currency. It can include business and legal documents, credit cards, checks, other financial media, art, antiquity materials, and documented security threats to person(s) and/or institutions.
The loss of valuable resources, man-hours, and associated assets due to fraudulent documents and financial media are escalating daily in the United States and other parts of the world. Part of the problem is that there are no predominantly established, widely accepted protocols between government agencies, business, and academia to prove authenticity. The primary difficulty stems from a lack of an instrumental solution. Currently there is no automated mechanism or method to analyze documents or financial media which takes into account accurate age-dating, the precise matching of varying ink samples, and alteration of a genuine article. Every year, hundreds of thousands of working hours are devoted to analyzing documents and financial media in order to curb the billions of dollars of losses in the domestic and international markets. The incurred monetary loss is mainly due to check, credit card, and paper currency fraud.
Unfortunately, technology which is available to the average consumer continues to remain on par with the processes used to create original financial media and assorted legal documentation by both government and corporations. Color copiers, scanners, multimedia software, laser printers, and desktop publishing software are among the tools which modern day criminals can use to create a forgery. Local, state, and federal law enforcement agencies as well as financial institutions are calling for an automated mechanism or method by which the expedient authentication of legal and financial documents, and documents threatening persons or institutional security can be established. Accordingly, a need exists to provide a method and system to aid in the verification of documents and other media.
Historically, a variety of techniques have been used for the analysis of inks, dyes, thin films, plastics, and written materials. One easy technique to thwart counterfeiting was the use of multicolor printing. This technique, although useful, is not without its shortcomings. The wide availability of color printers and especially full color copiers has greatly reduced the effectiveness of multicolor printing to stem counterfeiting.
Other techniques for the analysis of inks, dyes, thin films, plastics, and written materials are adaptations of classical wet chemistry analysis where a document or ink sample is subjected to a variety of solvents and chemically reactive agents. These chemical reactions are then compared to a known sample using the human eye and microscopic examination. Other forms of wet chemistry analyses involve spot tests on inks and documents which incorporate a light source to excite various chemicals. While useful, these classical wet chemistry analyses suffer from several shortcomings.
First, these classical wet chemistry analyses have proven to be highly unreliable as they involve personal, subjective judgements; even the opinions of experts may vary from one to another. Second, these techniques can not accurately distinguish between different samples of ink. Third, the use of wet chemistry techniques can not age-date within a single sample of ink. Fourth, these techniques do not provide a method to determine the origin of the document. Fifth, the use of these wet chemistry techniques is destructive and therefore makes the analysis difficult to repeat when necessary. Destructive techniques are highly undesirable, especially for application on rare or historic documents, and on evidence used in trials. Sixth, the use of classic wet chemistry is cumbersome because it requires hand-to-sample manipulation. A wide range of chemical tests have been developed during this century, but none have proven accurate over a range of samples. Most of these tests are micro-scale. This makes them difficult to perform, difficult to repeat, destructive in almost all cases, and subject to wide variety of environmental contamination. Seventh, few forensic methods have been developed to calibrate these tests. For example, thin-layer chromatography (TLC) has been used to analyze very small flakes of ink and dyes, but this technique, at best, is merely qualitative, not quantitative. Eighth, and perhaps most important, forgers have developed techniques to overcome wet chemistry analysis.
Inks, dyes, thin films, plastics, and written materials can be analyzed using automated comparison which incorporates spectral analysis using light sources of different wavelengths. However, this suffers from several major problems: wavelengths are polychromatic, energy is either too high or too low and the final examination has to be done by eyesight once again. Even when the best light sources are used, such as lasers, in conjunction with the best detectors, the results are still qualitative, not quantitative, due to damage to the sample from analysis, or the lack of any standards for comparison. Moreover, the current spectral analysis of credit cards suffers from several weaknesses. There is the destruction of the sample as well as the inability to differentiate between a genuine card and a genuine card that has been altered (as opposed to a total forgery). Document analysis has attempted to develop techniques for age dating using basic chemistry, but this is simply not sophisticated enough.
One technique for the analysis of inks, dyes, thin films, plastics, and written materials is scanning electron microscopy-electron diffraction x-rays (SEM-EDX). The technique of SEM-EDX overcomes some of the problems with earlier techniques, but still suffers from shortcomings. First, SEM-EDX is not accurate due to a wide variety of environmental contamination such as particulate matter. This contamination interferes with the accurate microscopic compositional sample determination. Second, with SEM-EDX, there is almost no spatial accuracy for differing elemental concentrations at the sub-micron level. Third, although SEM-EDX is used to determine specific elements present qualitatively, the SEM-EDX technique cannot distinguish on a small scale the precise location of a quantitative amount. Fourth, SEM-EDX cannot determine organic species, which comprises the majority of the samples used in document authentication and financial instruments.
Another technique for the analysis of inks, dyes, thin films, plastics, and written materials is magnetic ink character recognition (MICR) analysis. However, MICR cannot be used for the analysis of financial media and many identification systems because such documentation uses strips of magnetic material for information storage. An analysis conducted using MICR would destroy stored material within the magnetic strip, and in turn, the magnetic material would provide questionable results.
Recently, a new technique incorporating Raman spectroscopy has been used for the analysis of art work, ancient documentation, as well as more recently printed material. The Raman analysis of art has not yet proven itself quantitative nor has it been optimized for non-metallic species (organic). In addition, current Raman technology developed specifically for the analysis of inks and dyes (FNF Foram 6500) is also incapable of quantitative analysis, possibly destructive, and subject to fluorescence and back-scattering interference.
The main problems that all previously mentioned techniques suffer from are an inability to yield quantitative measurements in either elemental or molecular analysis, a destruction of evidence, the inability to determine that degree of destructiveness, and the inability to distinguish between molecular or oxidation states which makes age verification and artificial aging detection by photolysis or heat impossible. These techniques are inaccurate because their produced results are not quantifiable. They are cumbersome in that they require hand-to-sample manipulation on written words and because they lack spectroscopic inter-comparison. Hence, the need exists for an apparatus to perform a quantitative, non-destructive, accurate, precise (reproducible across a range of samples), elemental and molecular specific, analysis of inks, dyes, thin films, plastics, toners, papers, fixatives, paints, printing agents, and other written materials.